What is the legal basis for immigration law enforcement, besides the Constitution?

1. Statutes are the primary legal scaffolding: Congress wrote the rules

Congress has enacted comprehensive immigration statutes collected mainly in Title 8 of the U.S. Code that define who may enter and remain, create removal grounds, authorize detention and parole, and set enforcement mechanisms—these statutory provisions are the core legal basis enabling federal agencies and officers to detain, arrest, and remove noncitizens ^{[1] [5] [6]}.

2. Agencies implement and operationalize statutory grants of power

Because Congress “need only delineate basic policy,” courts have recognized broad delegations allowing executive agencies—principally the Department of Homeland Security and its components like ICE—to adopt regulations, procedures, and administrative mechanisms to implement immigration statutes, giving agencies significant discretion in enforcement practice ^[2].

3. Specific statutory authorities enable arrests, detainers, parole, and detention

Statutes and regulations specifically authorize administrative arrests (including warrantless arrests under immigration provisions), issuance of nonbinding detainers for local custody, parole of certain noncitizens for humanitarian or significant public benefit reasons, and detention pending removal, though courts have read temporal or other limits into detention statutes to avoid constitutional problems ^{[7] [8] [5]}.

4. Courts provide a body of precedent that both empowers and constrains enforcement

The Supreme Court and lower courts have historically given Congress wide latitude—often described as the “plenary” or exclusive federal control over immigration—upholding removal and exclusion authority while carving out constitutional protections and narrow review where appropriate; that jurisprudence is the interpretive framework that turns statutory text into enforceable power with limits ^{[2] [9]}.

5. Federal supremacy governs conflicts with state law, but anti‑commandeering limits federal reach into state policing

Where state law conflicts with federal immigration law, Congress’s power to preempt under the Supremacy Clause supports federal primacy; yet the Tenth Amendment and anti‑commandeering doctrine prevent the federal government from forcing states or localities to perform federal enforcement duties, creating a practical limit on how Congress or federal agencies can rely on state actors ^{[3] [4] [8]}.

6. Statutory process rights and administrative adjudication structure enforcement outcomes

Beyond constitutional guarantees, statutes govern procedural protections in removal proceedings—statutory notice requirements, rights to examine and present evidence in immigration court, and administrative rules that distinguish civil removal from criminal prosecution—which shape the mechanics by which enforcement decisions are made and reviewed ^[6].

7. Tensions, politics, and hidden agendas shape how statutory powers are used

Although the legal architecture is statutory and administrative, political choices—through executive action, grant conditions, and litigation—determine enforcement priorities and tactics; some actors seek to expand federal leverage (for example via conditional grants or interagency deployments), while others invoke constitutional or statutory limits to resist coercion, so legal texts are applied against a charged policy terrain where each party has strategic incentives ^{[10] [4]}.

8. What the sources do not settle

The materials show where the statutory and judicial bases lie and where constitutional limits are read in, but they do not resolve every open question—such as how far Congress could lawfully condition federal funds before coercion doctrines bite, or the precise contours of agency arrest discretion in every factual setting—so some operational limits remain contested in courts and politics ^{[10] [4]}.